The present invention relates to a catalyst for producing an epoxy compound and a method of producing an epoxy compound using the same. More particularly, it relates to a catalyst for producing an epoxy compound by catalytically oxidizing a compound having at least one ethylenic double bond with an oxidizing agent and to a method of producing an epoxy compound using said catalyst.
Epoxy compounds (epoxides) are compounds useful as intermediates or raw materials for the production of various industrial products. As actual examples of the production of industrial products using epoxy compounds as intermediates, there may be mentioned the conversion of ethylene oxide into ethylene glycol or polyethylene glycol, and the formation of polyether polyols such as polypropylene polyethers by alkoxylation of alcohols with propylene oxide. The thus-produced industrial products are consumed in large amounts in the production of polyurethanes and synthetic elastomers.
Epoxy compounds also serve as important intermediates for the production of alkylene glycols, such as propylene glycol and dipropylene glycol, and alkanolamines, which are among important industrial products as raw materials of solvents and surfactants.
As a method of synthesizing epoxy compounds, there may be mentioned, the epoxidation reaction of compounds having an ethylenic double bond, for example olefins, and this is one of commercially important chemical conversion methods. In this synthetic method, epoxy compounds are synthesized by adding one oxygen atom to the carbonxe2x80x94carbon double bond and, for producing ethylene oxide from ethylene, for instance, the method using a silver catalyst is well known and, for producing propylene oxide from propylene, the chlorohydrin method or the Halcon process using an organic hydroperoxide is well known. These methods have been put to practical use on commercially. However, the chlorohydrin method, for instance, has the problem of generation of a low concentration hydrogen chloride vapor.
In such epoxidation reaction, an olefin is converted to an epoxy compound using hydrogen peroxide as an oxidizing agent, and the use, as catalysts, of heteropolyoxometalates having a structure such that there is a heteroatom at the center with polyatoms coordinated to the heteroatom each via an oxygen atom is now studied. As for heteropolyoxometalates which are used as catalysts, it is known that ones having a defectivee structure lacking in an atom or atoms which should normally occur in the crystal structure and containing a metal element, namely ones resulting from substitution of polyatom with other metal element show catalytic activity.
Regarding such metal-containing heteropolyoxometalates, the following studies are carried out.
As an example of the use of one defective type heteropolyoxometalates as catalysts, J. Mol. Catal., A: Chemical, 108 (1996), p. 135-143 discloses an example of epoxidation of cyclohexene with hydrogen peroxide in the presence of a Cr-substituted one defective Keggin-structure heteropolytungstate [PW11O39]7xe2x88x92 catalyst, and J. Mol. Catal., A: Chemical, 117 (1997), p. 389-396 discloses a method of synthesizing the epoxide from cyclohexene and hydrogen peroxide using Fe(III), Cr(III), Ru(IV), Ti(IV) and V(IV) complexes of one defective type [PW11O39]7xe2x88x92 as catalysts. However, even when these catalysts are used, the epoxide namely epoxycyclohexane yield was low.
As an example of the use of two defective type heteropolyoxometalates as catalysts, there is the following disclosure. Thus, J. Catal., 182 (1999), p. 285-288 discloses an example of the epoxidation reaction of olefins such as cyclooctene and 2-octene with hydrogen peroxide using, as catalysts, two defective Keggin-structure silicotungstate species respectively substituted by the cations Fe, Mn and Cu. However, in spite of the olefin being cyclooctene, the catalytic activities are low. In particular when the proportion of hydrogen peroxide relative to the olefin becomes high, the utilization efficiency of hydrogen peroxide decreases markedly.
J. Am. Chem. Soc., 117, p. 681 discloses Ti- or V-substituted two defective type catalysts K7[PTi2W10O40] and H5[PV2Mo10O39]. However, in the reactions using such Ti- or V-substituted catalysts containing phosphorus as the heteroatom, the epoxidiation activity was very low.
J. Mol. Catal., A: Chemical, 114 (1996), p. 237-245, and 142 (1999), p. 61-76 respectively disclose a method of epoxidizing cyclooctene with hydrogen peroxide using Ti-substituted one defective and two defective type heteropolyacids [PTiW11O40]5xe2x88x92 and [PTi2W10O40]7xe2x88x92 catalysts. However, the productivity of the epoxide was low.
Further, as an example of the use of lanthanoid-containing defective type heteropolyoxometalates as catalysts, Bull. Chem. Soc. Jpn, 66 (1993), p. 2790-2796 discloses a heteropolytungstolanthanate anion catalyst represented by (M(Ce,Nd,Sm)W10O36;LnW10). In this case, the anion has the Weakley structure, and the lanthanoids(III) are coordinated to the polyacid W5O18. However, there is no olefin oxidation example.
Kidorui, 30 (1997), p. 288-289 discloses an epoxidation reaction of allyl alcohols by oxidation with hydrogen peroxide using a Weakley-structure heteropolyacid containing rare earth elements with lanthanoid elements(III) as core elements. The structure of this polyacid is not the so-called Keggin structure. Further, Kidorui, 16 (1990), p. 46-47 discloses the synthesis of a tetravalent terbium-substituted one defective type heteropolyacid [PW11O39]7xe2x88x92.
Polyhedron, 15 (1996), p. 3493-3500 discloses an example of the epoxidation reaction of cyclooctene with hydrogen peroxide using, as catalysts, lanthanoid-containing Weakley-structure heteropolyacids, namely [LnW10O36]9xe2x88x92 and [Ln{PW11O39}2]11xe2x88x92, or lanthanoid polyoxotungstate. The productivity of the epoxide is fairly high. However, there is no disclosure concerning polyoxometallates having the two defective type Keggin structure.
Indian J. Chem., 37A (1998), p. 816-819 discloses a Ln(La,Pr,Nd,Sm,Gd) metal-substituted one defective Keggin-structure heteropolyacid, [Ln(PW11O39)2]. However, there is no olefin epoxidation example.
Radiochemistry, 41 (1999), p. 1-23 discloses one defective type Keggin-structure and one defective Dawson-structure polyoxometallates as lanthanoid polyoxometallates. However, there is no example disclosed of the two defective type.
In the above study examples, the investigations concerning the application of heteropolyoxometalates to the epoxidation reaction remain insufficient. Thus, when heteropolyoxometalates are applied to the epoxidation reaction, their catalytic activity and the utilization efficiency of the oxidizing agent are insufficient, so that there is room for contrivance for rendering them suited as catalysts for the epoxidation reaction of olefins and the like, which is a method of producing commercially important epoxy compounds.
It is an object of the present invention, which has been made in view of the above-mentioned state of the art, to provide a catalyst capable of producing an epoxy compound in high yield and improving the utilization efficiency of the oxidizing agent on the occasion of catalytically oxidizing a compound having at least one ethylenic double bond with an oxidizing agent such as hydrogen peroxide to produce the corresponding epoxy compound, as well as a method of producing an epoxy compound using that catalyst.
The present inventors made various investigations in search of catalysts for producing an epoxy compound by oxidizing a compound having at least one ethylenic double bond with an oxidizing agent and, as a result, noticed that heteropolyoxometalates are useful commercially and found that
(1) a catalyst which comprising a polyatom-containing heteropolyoxometalate anion (A1) having two defective and/or three defective structure sites and containing a silicon atom as a heteroatom, and a specific element (E1),
(2) a catalyst which comprising a heteropolyoxometalate anion (A2) containing phosphorus as a heteroatom and molybdenum and/or tungsten as a polyatom and having two defective and/or three defective structure sites, and a specific element (E2), and
(3) a catalyst which comprising a heteropolyoxometalate anion (A3) containing phosphorus as a heteroatom and tungsten as a polyatom and having two defective and/or three defective structure sites, and a specific element (E3) are suited for use in the above oxidation reaction to produce an epoxy compound in high yield while improving the utilization efficiency of the oxidizing agent. They also found that such heteropolyoxometalate anions, when they are Keggin-structure heteropolyoxometalate anions having a specific structure, can produce their effects as catalysts in the above epoxidation reaction to more satisfactory extent. So, they have now completed the present invention.
Thus, the present invention provides a catalyst for producing an epoxy compound by oxidizing a compound having at least one ethylenic double bond with an oxidizing agent,
which comprises a polyatom-containing heteropolyoxometalate anion (A1) having two defective and/or three defective structure sites and containing silicon as a heteroatom, and
an element (E1) being at least one element selected from the group consisting of vanadium, tantalum, niobium, antimony, bismuth, chromium, molybdenum, selenium, tellurium, rhenium, cobalt, nickel, ruthenium, rhodium, palladium, osmium, platinum, iridium, silver, gold, zinc, aluminum, gallium, indium, scandium, yttrium, titanium, zirconium, hafnium, germanium, tin and lanthanoids, and being different from the polyatom.
The invention also provides a catalyst for producing an epoxy compound by oxidizing a compound having at least one ethylenic double bond with an oxidizing agent,
which comprises a heteropolyoxometalate-anion (A2) containing phosphorus as a heteroatom and molybdenum and/or tungsten as a polyatom and having two defective and/or three defective structure sites and
an element (E2) being at least one element selected from the group consisting of elements of the fourth to sixth periods of group IIIa, elements of the fourth to sixth periods of groups VIa to VIII, elements of the fourth to sixth periods of groups Ib to IIb, elements of the third to sixth periods of group IIIb, and elements of the fourth to sixth periods of groups IVb to Vb of the periodic table, and being different from the polyatom.
The present invention further provides a catalyst for producing an epoxy compound by oxidizing a compound having at least one ethylenic double bond with an oxidizing agent,
which comprises a heteropolyoxometalate anion (A3) containing phosphorus as a heteroatom and tungsten as a polyatom and having two defective and/or three defective structure sites, and
an element (E3) being at least one element selected from the group consisting of elements of the fourth to sixth periods of group Va.
The invention is also directed to a method of producing an epoxy compound by oxidizing a compound having at least one ethylenic double bond with an oxidizing agent,
wherein said method of producing the epoxy compound comprises using one of the above-mentioned catalysts.
In the following, the present invention is described in detail.